1. Field of the Invention
The present invention relates to an inductive-type thin-film magnetic head and a magnetic storage apparatus using the magnetic head.
2. Description of the Prior Art
The recording density of a hard disk drive has been remarkably improved. The recording density from 1990 downward tends to rise at an annual rate of approx. 60%. To improve the recording density of a hard disk drive, it is necessary to improve the recording track density by decreasing the track width of a magnetic head. Moreover, to improve the recording density, it is also important to improve the recording bit density. To improve the recording bit density, it is necessary to increase the coercive force (Hc) of a magnetic storage medium. Moreover, to write data in a high-Hc magnetic storage medium, an inductive recording head having a high recording capacity is necessary. Furthermore, to efficiently detect a signal output from a micro-scaled recording bit, an MR reproducing head is necessary. Therefore, an MR-inductive composite-type thin-film magnetic head constituted by combining an MR reproducing head with an inductive recording head is prospective for high-density recording.
FIG. 11 is a sectional view showing a conventional thin-film magnetic head. The thin-film magnetic head will be described below by referring to FIG. 11.
The conventional thin-film magnetic head 70 is produced by forming a lower shielding layer 74, a read gap layer 80 holding an MR magnetosensitive element 78 facing to an ABS plane 76, a shared pole layer 82 serving as an upper shielding layer and a lower pole layer, and a write gap layer 84 laminated in order on an insulating substrate 72; by forming a first flattening layer 86, a coil pattern layer 88, and a second flattening layer 90 laminated in order on the write gap layer 84 excluding the vicinity of the ABS plane 76; and by forming an upper pole layer 92 on the write gap layer 84, first flattening layer 86, and second flattening layer 90 nearby the ABS plane 76.
The shared pole layer 82 serves as an upper shielding layer for improving the reproducing resolution of an MR reproducing head and a lower pole layer of an inductive recording head. The MR magnetosensitive element 78 detects a signal magnetic field outputted from a not-illustrated magnetic storage medium facing to the ABS plane 76. The thickness of the write gap layer 84 serves as the gap of the inductive recording head. The first flattening layer 86 serves as the insulating base of the coil pattern layer 88 and the second flattening layer 90 smoothens the irregularity in height of the coil pattern layer 88. A portion on the write gap layer 84 nearby the ABS plane 76 where there is no first flattening layer 86 determines the gap depth D of an inductive recording head. A recording track width is determined by the front end portion width W (not illustrated) of the upper pole layer 92. The front end portion width W represents the width of the upper pole layer 92 along the ABS plane 76 (front end) in the direction vertical to the drawing plane, which is shown in FIG. 2 or the like.
To improve the recording capacity for high-density recording, it is preferable to set the gap depth D to a small value of approx. 1 [micron meter] or less. Moreover, to correspond to high-density recording, it is preferable to realize an upper pole layer 92 having a minimum front end portion width W. Furthermore, because a recording/reproducing data transfer rate is raised as a recording density (particularly, linear recording density) rises, a high speed recording capacity is required for a magnetic head for high-density recording.
Moreover, Japanese Patent Application Laid-Open No. 4-285711 discloses an invention for accurately forming a very-small-width magnetic-pole front end portion of a magnetic recording/reproducing thin-film magnetic head. Specifically, the front end portion of a lower magnetic pole and that of an upper magnetic pole are simultaneously formed on a lower magnetic-pole layer, gap layer, and upper magnetic-pole layer formed on a substrate through simultaneous ion etching by using a mask corresponding to the shape of a magnetic-pole front end portion. Then, a thin-film coil and an insulating film are formed to form the rear of an upper magnetic pole.
Furthermore, Japanese Patent Application Laid-Open No. 7-192222 discloses a thin-film magnetic head capable of effectuating a high-density recording/reproducing characteristic and an overwriting characteristic for data write. In this case, among gaps formed on a pole portion, a pole front end portion is formed into a narrow gap and the innermost side of the pole portion is formed into a wide gap g2.
Furthermore, Japanese Patent Application Laid-Open No. 9-237407 discloses a thin-film magnetic head capable of realizing higher density recording by reducing the number of magnetic fields generated at the lateral side of a magnetic pole and controlling the write spread and moreover, controlling the eddy-current loss when raising a recording frequency. In this case, the cross section of an upper magnetic pole is formed into a trapezoid and the major side is set so as to face a lower magnetic pole (upper shielding layer). Moreover, an upper magnetic pole is formed into a two-layer structure, the first layer of a lower magnetic pole is formed of a magnetic material having a large residual flux density, magnetic permeability, and resistivity (e.g. FeN, FeNZr, or FeNNb) and the second layer of it is formed of permalloy.
The first problem is that a pattern accuracy enough to decrease a gap depth D and a front end portion width W is not obtained. The first problem will be described below in detail using FIG. 1.
To form a necessary gap depth D, the first flattening layer 86, which defines the gap depth D, must be considerably nearing the ABS plane 76. Therefore, the conventional thin-film magnetic head 70 had the following problem in order to form a resist frame pattern (not illustrated) for forming the upper pole layer 92 through the frame plating method.
The first flattening layer 86, coil pattern layer 88, and second flattening layer 90 are laminated in order and then, a resist frame pattern is formed. In this case, a large height difference is formed between the write gap layer 84 and the second flattening layer 90 at the front end portion. Therefore, the film thickness of the resist frame pattern at the front end portion becomes 10 (micron meter) or more and thereby, the accuracy for forming a thin pattern through photo lithography process is deteriorated. Moreover, front end sides of the first flattening layer 86 and second flattening layer 90 are respectively formed like a curved surface. Therefore, light for exposure in photo lithography process reflects on the curved surface and thereby, the vicinity of the ABS plane 76 of the resist frame pattern is easily overexposed.
As a result, the resist frame pattern for forming the front end portion of the upper pole layer 92 has a large film thickness and it is partially overexposed. Thereby, a narrow track pattern cannot be obtained. Thus, to obtain a preferable gap depth D, it is difficult to obtain a preferable front end portion width W.
The second problem is that the high-frequency characteristic is deteriorated to decrease the front end portion width W, that is, the track width. The second problem is described below in detail.
FIGS. 12(a) and 12(b) are illustrations showing magnetic domains of magnetic thin films. FIG. 13 is a graph showing the frequency dependency of the magnetic permeability of a magnetic thin film. The second problem will be described below by referring to FIG. 11 to FIG. 13.
The frequency response of the recording/reproducing characteristic of the thin-film magnetic head 70 greatly depends on the shape of the recording-pole magnetic domain of the head 70. As shown in FIGS. 12(a) and 12(b), the magnetic permeability of a sheet-like magnetic thin film 100 greatly depends on the direction of magnetic easy axis 102 of the magnetic thin film 100 and the direction of an externally applied signal magnetic field 110. The magnetic domain structure in the magnetic thin film 100 has closure domain structure in which a magnetic domain 106a having a magnetizing direction 104a parallel with magnetic easy axis 102 occupies the most part and a triangular magnetic domain 106b having a magnetizing direction 104b vertical to magnetic easy axis 102 is adjacent to the magnetic domain 106a so that a magnetic field does not exit to the end of a magnetic thin-film pattern. The boundary between the magnetic domains 106a and 106b is a magnetic domain wall 108.
As shown in FIG. 12(a), the case in which magnetic easy axis 102 is perpendicular to the signal magnetic field 110 is referred to as xe2x80x9cmagnetization rotation mode.xe2x80x9d As shown in FIG. 12(b), the case in which magnetic easy axis 102 is parallel with the signal magnetic field 110 is referred to as xe2x80x9cmagnetic-domain-wall moving mode.xe2x80x9d As shown in FIG. 13, the magnetization rotation mode is superior to the magnetic domain wall mode in high-frequency characteristic by approx. order of two. This is because the rotational speed of magnetization is higher than the moving speed of a magnetic domain wall by order of two to three.
The above mentioned, a conventional-thin-film magnetic head is shown in FIG. 6.29 (p. 6.34) and FIG. 6.30 (p. 6.35) of xe2x80x9cMagnetic Recording Technology, Second Edition (issued in 1996)xe2x80x9d edited by C. D. Mee and E. D. Daniel, issued by MacGraw Hill, Inc., wherein a magnetic domain structure has a magnetic anisotropy vertical to a signal magnetic field and the magnetizing direction vertical to the signal magnetic field at the front end portion of a recording pole.
FIGS. 14(a) and 14(b) are illustrations showing the magnetic domain structure of a conventional thin-film magnetic head, in which FIG. 14(a) is a plan view and FIG. 14(b) is a front view. FIGS. 15(a) and 15(b) are illustrations showing the magnetic domain structure of a conventional thin-film magnetic head for narrow tracks, in which FIG. 15(a) is a plan view and FIG. 15(b) is a front view. The magnetic domain structures are described below by referring to FIGS. 11, 14, and 15.
As shown in FIGS. 14(a) and 14(b), in a thin-film magnetic head 70, magnetic domain structures of a shared pole layer 82 and an upper pole layer 92 are formed so that magnetic easy axis 102 is perpendicular to a signal magnetic field 110. Thereby, a magnetization rotation mode is realized.
As shown in FIGS. 15(a) and 15(b), however, when the recording track width decreases, a magnetizing direction is set along the pattern end at the front end portion of the upper pole layer 92 even if magnetic easy axis 102 is vertical to the signal magnetic field 110 in order to prevent the number of demagnetization fields at the pattern end from increasing. With the magnetic domain structure having the front end portion of the upper pole layer 92 described above, the response of magnetization for the signal magnetic field 110 becomes the magnetic-domain-wall moving mode and thereby, the high-frequency characteristic is deteriorated.
Therefore, it is an object of the present invention to provide a thin-film magnetic head capable of accurately decreasing a gap depth D and a front end portion width W without deteriorating any high-frequency characteristic due to decrease of a track width and to provide a magnetic storage apparatus using the thin-film magnetic head.
A thin-film magnetic head of the present invention is produced by forming a lower pole layer, a write gap layer, and an upper pole layer laminated in order along an ABS plane. Moreover, the upper pole layer is configured from a front end portion facing to the ABS plane and a yoke portion connected to the front end portion through a junction, magnetic easy axis of the front end portion on the ABS plane is oriented in the film thickness direction of the front end portion. Magnetic easy axis of the front end portion of the upper pole layer is vertical to a signal magnetic field because the axis is oriented in the film thickness direction of the front end portion. Therefore, the recording frequency response is dominated by the magnetization rotation mode.
The thin-film magnetic head in claim 2 is produced by forming a lower pole layer, a first flattening layer, a coil pattern layer, and a second flattening layer laminated in order on the write gap layer excluding the vicinity of an ABS plane, and by forming an upper pole layer on the write gap layer nearby the ABS plane. Moreover, the upper pole layer is configured from a front end portion facing to the ABS plane and a yoke portion connected to the front end portion through a junction, magnetic easy axis of the front end portion on the ABS plane is oriented in the film thickness direction of the front end portion, a concave portion is formed in the lower pole layer at a position separated from the ABS plane, the concave portion is filled with a nonmagnetic material, and the gap depth between the upper pole layer and the lower pole layer is determined by the concave portion.
The gap depth is determined not by the distance from the ABS plane to the front end of the first flattening layer but by the distance from the ABS plane to the margin of the concave portion. Because the concave portion is formed in a flat lower pole layer, no problem occurs in the photolithography process for forming the concave portion. Moreover, a resist frame pattern for forming the front end portion of the upper pole layer is not increased in film thickness or it is not overexposed because the first flattening layer can be sufficiently separated from the ABS plane. Therefore, it is possible to decrease the width of the front end portion of the upper pole layer. Even if decreasing the width, the frequency response for recording becomes the magnetization rotation mode because of the above reason.
The thin-film magnetic head in claim 3 is produced by forming a lower shielding layer, read gap layer holding an MR magnetosensitive element facing to an ABS plane, a shared pole layer serving as an upper shielding layer and a lower shielding layer, and write gap layer laminated in order on an insulating substrate, by forming a first flattening layer, a coil pattern layer, and a second flattening layer laminated in order on the write gap layer, and by forming an upper pole layer on the write gap layer at least nearby the ABS plane. Moreover, the upper pole layer is configured of a front end portion facing to the ABS plane and a yoke portion connected to the front end portion through a junction, magnetic easy axis of the front end portion on the ABS plane is oriented in the film thickness direction of the front end portion, a concave portion is formed on the shared pole layer at a position separated from the ABS plane, the concave portion is filled with a nonmagnetic material, and the gap depth between the upper pole layer and the lower pole layer is determined by the concave portion. That is, the thin-film magnetic head of claim 3 is an MR-inductive composite-type thin-film magnetic head constituted by combining an MR reproducing head with an inductive recording head.
Thin-film magnetic heads in claims 4 to 19 are respectively configured by restricting some of the components of the thin-film magnetic head in claim 1, 2, or 3. Magnetic storage apparatus in claims 20 to 25 are respectively configured by using the thin-film magnetic head in claim 1, 2, or 3.
The thin-film magnetic head in claim 4 uses the thin-film magnetic head in claim 3 in which the MR magnetosensitive element is the GMR type. The GMR magnetosensitive element is produced by forming of a Ta film (3 nm), an NiFe film (8 nm), a CoFe film (1 nm), a Cu film (2.5 nm), a CoFe film (3 nm), and NiMn film (30 nm) laminated in order on the lower shielding layer side. The MR magnetosensitive element has a magneto-resistance ratio of approx. 5% that is approx. two times larger than that of a conventional MR magnetosensitive component and therefore, suitable for a narrow-track high-density reproducing magnetic head.
As for the thin-film magnetic head in claim 5, the lower shielding layer of the thin-film magnetic head of claim 3 is formed through the sputtering method. The lower shielding layer, for example, is formed by forming an amorphous CoTaMo film through sputtering and heat-treating the film in an anisotropy-providing magnetic field at 350 [degrees centigrade], and then forming a shielding pattern shape through ion milling. When the lower shielding layer uses a sputtered film, the surface of the film is smoother than that of an NiFe film formed through the plating method because the crystal grain size is smaller than that of the NiFe film. Therefore, the characteristic of an MR magnetosensitive element formed on the lower shielding layer is improved.
The thin-film magnetic head in claim 6 uses the thin-film magnetic head in claim 1, 2, or 3 in which the front end portion of the upper pole layer is made of a material having a saturation flux density of at least 1.6 T or more. This type of the material includes a CoFeNi-based material having a saturation flux density of 1.8 T or more. Therefore, it is possible to compensate decrease in recording magnetic field strength generated due to decrease of a recording track width and realize a magnetic head suitable for narrow-track recording.
As for the thin-film magnetic head in claim 1, 2, or 3, the film thickness of the front end portion on the ABS plane is assumed as t and the front end portion width vertical to the film thickness t is assumed as W. An inequality of t greater than W is effectuated for the thin-film magnetic head of claim 7 and an inequality of t greater than 3 W is effectuated for the thin-film magnetic head of claim 8. When the inequality of t greater than W is effectuated, the shape anisotropy due to the difference between demagnetization fields is formed in the film thickness direction. To form magnetic easy axis due to the shape anisotropy in the film thickness direction, it is preferable that the inequality of t greater than 3 W is effectuated when considering an intrinsic magnetic anisotropy and a strain induction anisotropy due to a stress of a pole height lapping or the like.